Machine vision is based on a complex algorithm, they don't see things like we do, but the process they use to learn how to see things is both very similar and very different to how humans learn what things are.
Machines start by analyzing an image, they guess what it is, and then are told if they're right or wrong. If the computer is wrong, it will register that any image that looks like that is NOT what it thought it was, and is instead the correct answer. It will repeat this process over and over, until it has processed a whole bunch of images.
This process allows a computer to build a complex set of questions in its head. It will repeatedly ask itself, Does it look like this image I've seen before? and compare many different images until it makes its guess, then adds to its database. This means that its database is only as big as the amount of images it's been fed, and that it can easily make mistakes when there are images with a lot of similar features as one it's seen before.
In order to keep images from looking out of place, adding a border can help them feel more natural and integrated into your website! There are many different kinds of borders, and ways to add them, each one has a different effect. Always consider which one will help your image pop, without letting it be overwhelming.
Within your CSS there's a border property you can apply to images.
The border property allows you to change the color and specify where you want the border to appear!
For Example: border: #f24616 (This would make a red (#f24616 color) border around the image.
Along with that, the border-style property allows you to change the look of the border!
This allows you to make it dotted, dashed, 3-D looking, or other!